Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-40912 is a high-severity Use of Incorrectly-Resolved Name or Reference (CWE-706) vulnerability in Traefik Traefik. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception (T1034); ranked in the top 48% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-40912 is a high-severity authentication bypass vulnerability (CVSS 3.1 score of 8.2) affecting Traefik, an HTTP reverse proxy and load balancer. The issue resides in the StripPrefixRegex middleware when combined with ForwardAuth, BasicAuth, or DigestAuth, impacting versions prior to 2.11.43, 3.6.14, and 3.7.0-rc.2. Specifically, the middleware applies regex matching against the decoded URL path but uses the resulting byte length to slice the percent-encoded raw path. If a dot (or multiple dots) appears in the URL prefix, the stripped raw path becomes a dot-segment (e.g., /./admin/secret) per RFC 3986, which evades protection mechanisms.
An unauthenticated network attacker (AV:N/AC:L/PR:N) can exploit this by crafting a request with dots in the prefix portion of a protected URL path. The dot-segment path is forwarded in the X-Forwarded-Uri header to ForwardAuth, which fails to match it against protected patterns, allowing the request to proceed. The backend then normalizes the dot-segment to the actual protected path, resulting in unauthorized access to sensitive content (C:H/I:L/A:N). This works against any backend performing dot-segment normalization as defined in RFC 3986.
Traefik has addressed the vulnerability in patched releases: version 2.11.43, 3.6.14, and 3.7.0-rc.2. Security practitioners should upgrade immediately to these versions, as detailed in the official GitHub release notes and security advisory (GHSA-6jwx-7vp4-9847). The issue is linked to CWE-706 (Use of Incorrectly-Resolved Name Into a Reference Chain).
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-26428
Vulnerability Data
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's StripPrefixRegex middleware when used in combination with ForwardAuth, BasicAuth, or DigestAuth. The middleware matches…
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the regex against the decoded URL path but uses the resulting byte length to slice the percent-encoded raw path. When a dot (or multiple dots) appears in the prefix portion of the URL, the raw path after stripping becomes a dot-segment (e.g. /./admin/secret). ForwardAuth receives this dot-segment path in X-Forwarded-Uri, which does not match the protected path patterns and therefore allows the request through. The backend then normalizes the dot-segment to the real path per RFC 3986 and serves the protected content An unauthenticated attacker can exploit this against any backend that performs dot-segment normalization. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.3.2
Mitigating Controls (NIST 800-53 r5) AI
Enforces the intended directory access authorizations that path traversal would otherwise bypass.
Input validation directly neutralizes special path elements before pathname construction occurs.
Information flow enforcement can constrain flows that result from an incorrectly resolved name or reference.
Least privilege reduces the impact of any unauthorized file access obtained via traversal.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices directly prevent incorrect name/reference resolution bugs during coding.
Enforced authorization boundaries limit damage from an incorrectly resolved reference.
Logical segmentation and access controls reduce the chance an out-of-sphere resolution succeeds.
Hardened configuration baselines can constrain allowable name-to-resource mappings.
Patching/maintenance can remediate known path-traversal flaws in deployed software (partial prevention of exploitability) but does nothing to stop the coding defect from being introduced in the first place.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect incorrect name or reference resolution through fuzzing and negative test cases.
Network segmentation and routing policies reduce the chance that a mis-resolved name leads to an unintended external resource.
Segregated networks limit the blast radius when a name or reference resolves outside the intended control sphere.
Secure SDLC practices include design reviews that can catch incorrect name or reference handling before deployment.
Application security requirements can mandate validation of all external references and names used at runtime.
Secure architecture principles discourage reliance on ambient or globally-resolvable names without explicit scoping.